Many tools have parts that interact with each other through ball bearings. The ball is typically positioned within a groove or circular cavity and provides a rolling interface between two moving parts, reducing friction between the parts while still allowing relative movement.
For example, impact wrenches include a ball bearing interface between a cam shaft and hammer. The ball is inserted into straight or angled grooves that are defined along the exterior of the cam shaft, and interface with cooperative grooves in the hammer. One such cam shaft is shown in FIG. 5. This cam shaft 535 includes a base 540 and a shaft 545 extending from the base 540. The shaft 545 includes grooves 550 for receiving a ball bearing that interfaces with grooves in a hammer. The cam shaft 535 also includes holes 555 to receive fasteners, such as screws or nails, for attachment to other objects.
Prior art cam shafts 535 include grooves that include a vertex 560. When the impact wrench is dropped, the cam shaft 535 abruptly stops once it impacts the ground, and the deceleration forces move the balls to the vertex 560 of the cam shaft 535. At the same time, the hammer is movably disposed on the shaft 545 and moves axially against a spring, sliding over the ball bearings and allowing the ball bearings to disengage through an opening in the front face of the hammer, thus destroying the ball bearing system.